Pressure actuated by-pass valves



2,967,485 Patent-ed. Jan. 10, 1961 PRESSURE ACTUATED BY-PASS VALVESFrank Hathorn 'llowler, Dob Park, Otley, England, and

John Maurice Towier, deceased, late of Mayfair, London, England, byFrank Hathorn Towler, executor, Dob Park, Otley, England, assignors toElectraulic Presses Limited, Rodley, near Leeds, England, alimited-liability company of Great Britain Original application Dec. 4,1952, Ser. No. 324,104,

new Patent No. 2,805,038, dated Sept. 3, 1957. Divided and thisapplication Jan. 3, 1957, Ser. No. 632,341

Claims priority, application Great Britain Dec. 7, 1951 Claims. (Cl.103-11) This invention relates to bypass valves of the type in whichfluid flow between inlet and outlet ports is controlled by an axiallymovable valve member or spindle, and it is more particular'y concernedwith by-pass valves in which the positioning of the movable valve memberis controlled by pressure fluid supplied from a source other than thatof the fluid by-passed by the valve. This invention is a division of ourcopending application, Serial No. 324,104, filed December 4, 1952, whichissued as Patent No. 2,805,038.

One object of the invention is to provide a 'by-pass valve of the abovegeneral character which is pertlcularly well adapted to provide forloadingand unloading a plurality of pumps in predetermined sequence toeliminate or reduce shock in the exhaust system. A' more specific objectis to provide a by-pass valve construction which permits a plurality ofsuch valves to be operatively connected in series relation to providefor sequential operation either to loading or unloading positions.

Other objects and advantages of the invention will become apparent fromthe following detailed description of the preferred embodimentsillustrated in the accompanying drawing.

In order that the invention may be clearly understood and carried intoeffect several examples of by-pass valve according to the presentinvention and the manner in which a series of the same may be used forloading and unloading an equivalent number of pumps in series will nowbe described by aid of the accompanying drawing in which: a

The figure is a diagram illustrating one manner of using four by-passvalves for loading and unloading in sequence four pumps.

Like parts throughout the views in the accompanying drawing will bedenoted by like reference numerals.

The valve illustrated in the drawing comprises a valve body 10, having abore within the interior of the valve body which is divided laterallyinto two portions or chambers 2 and 3 by a guide member 4, the portion 2forming a hydraulic cylinder for pilot pressure liquid and the otherportion 3 a bore proper for the slidable reception of a primary valvemember 5a. Within the hydraulic cylinder 2 is disposed a piston 6b forreciprocating movement therein, the pilot pressure liquid entering thecylinder 2 on one side of this piston 612 through an inlet 7. Fluid isexhausted from the opposite side of the piston through an outlet 8.

An inlet 10 and an outlet 11 in the valve body 1. for primary pressureliquid are connected by a passage 12 which is opened and closed by ahead or mitre valve 13 forming part of the valve member 5a. Extendingthrough the valve member 5a is a longitudinal passage 14- which allowsprimary pressure liquid to flow to the outlet 11 from a balancingchamber or space 15 on the opposite side of the valve member 5a.

Primary pressure liquid from the inlet 1d obtains an entry into thebalancing chamber 15 by way of a permanently open passage 16 ofrestricted area extending axially of the valve member 5a and its returnflow through the longitudinal passage 14 at a greater rate than throughthe passage 16 is controlled by a needle valve 17 slidable in an axialbore in the guide member 4 and having a tapered end which seats withinthe opposing end of the passage 14.

The object oi'the permanently open and restricted passage 16 is tomaintain a pressure balance on both sides of the primary valve member 5auntil this balance is upset upon the opening of the longitudinal passage14. The pressure stroke of the piston 6b is opposed by a spring 18 andsuch spring in this instance serves to move the piston to cause theneedle valve to open the passage 14. Upon the upset of the aforesaidpressure balance the primary valve member 5a is forced by the pressureat the inlet It) to follow the movement of the needle valve and in sodoing toopen the passage 12.

in the exemplary valve the pilot pressure liquid is admitted to thecylinder 2 above the piston 6b and the spring 18 is disposed within thepiston and seats against a pad 19 on the outer end of the needle valve17 whereby the same tends to lift the valve 17 from. its seat againstthe opposing pressure on the piston 6b.

A restricted by-pass between the pilot pressure inlet 7 and the exhaustpassage is formed by a hole 29 driled in the end cover of the valvebody, a plug 38 threaded into the hole and formed with an orifice 31,and a passage 32 drilled in the valve body. This is to enable pilotpressure liquid from the space on the outside of the piston 6b to escapeat a preterrnined rate into the outlet 8 to exhaust. The permitted rateof escape through the orifice 31 is such as will ensure the maintainingof a pressure on the outside of the piston which will over.- come theopposing pressure of the spring 18.

Thus with pilot pressure liquid admitted to the upper end of thecylinder 2 the passage 12 will be closed and upon interrupting theadmission of pilot pressure liquid to the cylinder 2 or if such supply.fails the spring 18 will carry theneedle valve 17 and the piston 6upwards or outwards ,at a rate which will be determined by the force ofthesspring 18 in relation tolthe combined area of the orifice 31. 7

In consequence of this upward or outward, movement of the needle valvethe same ,will be lifted from its seat and allow the pressure within thespace 15 to escape through the longitudinal passage 14. .As the rate ofthis escape will be greater than the rate at which liquid can enter thespace 15 up the restricted passage 16 the pressure balance on oppositeends of the valve member 511 will be upset andthis valve member willaccordingly follow the needle valve until they again meet and effectrecosing of the longitudinal passage 14 when the pres sure balance willonce more be restored. ln'this new position of the valve member 5a thepassage 12 connecting the inlet it? to the outlet 11 will be opened. Thespring 18 is designed to have considerable force in relation to thesmall force in the same direction which may be applied by pressureacting on the end of the needle valve or pilot spindle which projectsinto the space 15 so as to ensure that the rate of movement of the pilotspindle shall not be very materially afifected by variations of pressurewithin the body of the by-pass valve and it will be understood that therate of movement of the valve member 50 will be coincident therewith."

In the embodiment described above, it will be seen that the movement ofthe by-pass valve member 5a. in one direction or both directions may beeffected by the pressure of the primary fluid, which flows through andis controlled by the by-pass valve member, acting upon an area of theby-pass valve member, but in all cases the said movement is initiated bythe pilot-piston 6b actuated by pilot-pressure and it is controlled by aseparate pilot control valve not shown designed to admit or interruptthe admission of pilot-pressure to the pilot-piston. Thus, ifpilotpressure liquid is admitted to the pilot-piston at a suflicientrate, the velocity across the escape orifice 31 will be such as toincrease the pressure in the pilotcylinder so that it overcomes theforce of the pilot-spring 18 and forces the pilot-piston downwards,thereby causing the by-pass valve to close; and the rate of closing willbe determined by the rate at which pilot-pressure is supplied. On theother hand, if the supply of pilot-pressure is interrupted, thepilot-spring will immediately force the pilot piston upwards, therebycausing the by-pass valve to open; and the rate of opening will bedetermined by the area of the pilot-piston in relation to the area ofthe escape orifice 31 and the force of the pilot-spring. Furthermore, itwill be appreciated that the operation of the by-pass valve can becontrolled by a very simple pilot-control valve having only twooperative positions, open-closed, designed to admit and interrupt theflow of pilot-pressure liquid to the pilot-piston. The flow isunidirectional from pilot-control valve to pilot-piston, and the pipefriction can be taken care of by providing adequate pilot-pressure.Reverse flow is through the orifice 31 within the pilot-piston assemblyand therefore not affected by pipe friction and not very materiallyaffected by changes of viscosity of the pilot-pressure liquid. That isto say that the said orifice 31 is located within the pilot-piston orwithin the pilot-piston assembly, to permit a restricted flow of pilotpressure liquid from one side of the piston to the exhaust, so thatdisplacement of liquid takes place from the pilot-piston cylinder whenthe piston is moved by the pilot-spring and there is not materialdisplacement along the exhaust pipes except when the pilot piston isbeing moved downwards, and held at the lower end of its stroke by pilotpressure.

When two or more such by-pass valves are employed in a system forloading or unloading a similar number of pump units, the valves will beconnected in the manner shown in the figure. More particularly, pilotpressure oil is supplied directly to connection 7 of valve A only. Theconnection 7 of the valve B, on the other hand is connected to port 33of valve A which is connected by a drilled passage 34, and a radialpassage with an annular groove 38 in the piston chamber 2 adjacent itsupper end. Passage 34 is also in communication with the lower end of thechamber 2 by way of a restricted orifice 37. The orifice in this case isformed in a plug 35 threaded into the valve body. Valve C is similarlyconnected to valve B and valve D to valve C. It will also be noticedthat plug 30 incorporating orifice 31 is replaced on valves B, C, D,etc., with a solid plug 39'.

Thus when the pumps are required to be loaded at the commencement of apress cycle, pilot pressure oil will be supplied to 7 of valve A. Thiswill push the piston 6b downwards, which in turn will close the mitreseat on valve member 5a and load the pump unit controlled by valve A.When the piston 6b has covered the major portion of its stroke, saywithin of closing, the upper face of the piston 6b will enter in theannular groove 38. Thus pilot pressure oil can now proceed via annulargroove 38, drilled passage 34, connection 33 of by-pass valve A toconnection 7 of by-pass valve B. Valve B will now close in exactly thesame manner as valve A, and the pump unit controlled by valve B will bebrought on to load. Similarly pilot pressure oil is fed in turn toby-pass valve C, and D etc., and all the pumps in the system will bebrought in, in sequence, thus eliminating shock Waves in the system.

As previously stated, it is equally desirous to unload the pump units insequence, when the press cycle or part of the cycle has been completed,to avoid shocks in low pressure exhaust lines. As described when pilotpressure oil to the by-pass valve is interrupted, spring 18 will liftthe piston 6b and pilot spindle 17, liquid being displaced from thechamber above the piston, through the orifice 31.

The rate of lift, and consequently, the rate of opening of the mitreseated valve member 5a, depends upon the load of spring 18, and area oforifice 31.

It will be appreciated that when the mitre seated valve member 5a beginsto lift, high presure pump delivery, connected in at 10, can pass toexhaust via 11.

To achieve this sequence unloading, the first valve A has an orifice 31in the plug 30; in the following valves, however, the plug 39 is solid.

Thus, when the needle valve 17 and piston 6b of the first valve A haslifted approximately /8", the lower edge or skirt of the piston 6b willcommence to uncover the drilled passage containing the plug 35. Thispassage is connected by the orifice 37, drilled passage 34 andconnection 33 of valve A to connection 7 of valve B and thence to thechamber above the piston 6 of valve B.

Spring 18 of valve B will now be able to lift the piston 6b and pilotspindle 17 of valve B, displacing liquid from above the piston via theorifice 37 and connection 8 of valve A to exhaust.

Thus, the mitre seated valve member 5a of valve B will begin to lift,and the pump units controlled by valve B will commence to unload.Similarly, when the piston 6b has lifted approximately 4;", the pistonand spindle of valve C will commence to lift, and the pump units will beunloaded in sequence.

We claim as our invention:

1. In a hydraulic system including a plurality of continuously runningpressure fluid pumps, a by-pass valve for each pump normally operativeto unload the pump by diverting its delivery to exhaust, a pressurefluid operated controller for each valve, an inlet and an outlet forpressure fluid in each controller, said controllers being connected inseries with the pilot pressure outlet of the first valve controllerconnected to the pilot pressure inlet of the next valve controller inthe series and so on throughout the series, conduit means connected tothe inlet of the first valve controller for supplying thereto pilotpressure fluid to cause the controller to close the associated valve andinterrupt the diversion of the pump delivery to exhaust whereby to loadthe pump, said first valve controller and succeeding controllers actingupon operation to direct pilot pressure fluid to the succeedingcontroller to load the associated pumps in succession, said controllersacting upon interruption of the supply of pilot pressure fluid to allowthe associated valves to open and unload the pumps in the same order inwhich they were loaded.

2. A hydraulic system as defined in claim 1 in which the first actuatorof the series is provided with an orifice connected to continuouslybleed pilot pressure fluid therefrom so that a predetermined flow offluid is required to maintain the valve closed, and wherein that orificesimilarly coacts with the other actuators of the series when connectedto receive pilot pressure fluid.

3. A hydraulic system as defined in claim 1 in which the first actuatorof the series is provided with an orifice connected to exhaust fluidfrom that actuator and permit its return to rest position uponinterruption of the supply of pilot pressure fluid, and wherein eachactuator is arranged upon return to rest position to connect thesucceeding actuator for exhaust through said orifice.

4. A hydraulic system as defined in claim 1 in which additional means isincorporated in each actuator for initiating exhaust of fluid from thesucceeding actuator upon return of the preceding actuator to normalunoperated position.

5. In a hydraulic system including a plurality of continuously runningpressure fluid pumps, in combination, a like plurality of valves eachindividual to and connected with one of the pumps, each of said valvesbeing normally open and effective to divert the output of the associatedpump to an exhaust line, said valves when closed being operative tointerrupt the diversion of fluid and place the pumps on load, a pressurefluid operated controller for each valve including a cylinder with aworking piston reciprocal therein, means operatively connecting thepiston with the associated valve, spring means normally urging eachpiston in a direction to open the associated valve,

conduits connecting the controller cylinders in series, a 10 conduitconnected to the cylinder of the first controller of the series forsupplying pressure fluid thereto to shift the piston in a direction toclose the first valve, the conduits connecting the controller cylindersbeing related thereto so as to establish communication to each succeeding cylinder after the piston in the preceding cylinder ha: advanced apredetermined distance.

References Cited in the file of this patent UNITED STATES PATENTS1,002,306 Perkins Sept. 5, 1911 1,769,898 Mathews July 1, 1930 2,246,913Collins June 24, 1941 2,420,052 Muir May 6, 1947 2,617,361 Neal Nov. 11,1952 2,805,038 Towler et al. Sept. 3, 1957

